Foundations on large diameter bored piles in soft and medium dense non-cohesive soils will become more economic if the soil beneath the pile is densified and if the stiffness of the soil is measured in a real-time process. The process comprises several steps, among them a preliminary design, excavation to preliminary pile point elevation, dynamic treatment of the bottom of excavated borehole while acceleration/retardation and strains are recorded, and an iterative calculation of static deformability of the soil based on the dynamic deformability. The dynamic loading is transferred to the soil by means of a heavy ram dropped onto a steel body instrumented with accelerometers and strain gauges.